class_docstr: Abstract base class for strategies that fetch information about data issues.
  
  Subclasses must implement the `get_info` method, which takes a `Data` object, a dictionary of
  information about data issues, and an optional issue name, and returns a dictionary of
  information about the specified issue, augmented with dataset about the dataset as a whole.
  
  This class also provides a helper method, `_get_info_helper`, which takes an information
  dictionary and an optional issue name, and returns a copy of the information dictionary for
  the specified issue. If the issue name is `None`, this method returns `None`.
code: def _get_info_helper(
      info: Dict[str, Dict[str, Any]],
      issue_name: Optional[str] = None,
  ) -> Optional[Dict[str, Any]]:
      if issue_name is None:
          return None
      if issue_name not in info:
          raise ValueError(
              f"issue_name {issue_name} not found in self.info. These have not been computed yet."
          )
      info = info[issue_name].copy()
      return info
  
imports: from __future__ import annotations
  import warnings
  from abc import ABC, abstractmethod
  from typing import TYPE_CHECKING, Any, Dict, List, Optional, Union
  import numpy
  import pandas
label_desc: Use image node_id 2 for calling the _InfoStrategy obj's underlying member method code with example usage: obj._get_info_helper(info, issue_name) and returns: info, None